1. Field of the Invention
The invention relates to the field of cardiac leads and catheters, including pacemaker leads, defibrillator leads, ablation leads, mapping leads and the like, and in particular, to an apparatus and method for variably and controllably changing the curvature of the tip of such a cardiac lead.
2. Description of the Prior Art
Currently, during the implantation of a permanent cardiac pacemaker system, the leads are introduced into a vein either via a cut down or percutaneous sheath introduction and are positioned under fluoroscopy into either the right atrium, right ventricle, or both in the case of a dual chamber pacing system. The positioning of the pacemaker leads is the most time consuming and difficult aspect of the implantation. The current practice for lead placement requires the surgeon or cardiologist to advance the cardiac lead toward the heart through the veins until initial access is obtained. As the lead passes through the tributary veins into the subclavian vein and then into the right atrium of the heart, a straight stylet or wire must be disposed within a longitudinal lumen within the cardiac lead in order to give the lead sufficient strength and rigidity to proceed into the right atrium. An important aspect of proper placement is crossing of the tricuspid valve. In order to achieve this, the straight stylet is withdrawn and the physician fashions a curve at the tip of another stylet. Thereafter, most physicians continue advancing the lead with the curved tip stylet in place into the pulmonary artery outflow tract to confirm right ventricle access and to rule out the possibility of entrance into the coronary sinus or coronary vein, which can mimic the appearance of a right ventricle placement under fluoroscopy. Once the physician has confirmed that placement of the lead is in fact in the pulmonary outflow tract, the conventional practice requires the physician to then remove the curved stylet and partially readvance the original or another straight stylet into the lead. The cardiac lead is then carefully pulled back under direct fluoroscopic observation until the lead drops from the proximal portion of the pulmonary artery to the floor of the right ventricle, after which the physician advances the stylet to its fully advanced position within the lead to advance the lead to the distal most portion of the right ventricular apex.
In the case of atrial lead placement, the lead is then positioned into either the right atrial appendage or is fixed by means of an active fixation screw or tines into or near the septum or other portion of the atrium selected by the physician.
In the case where a ventricular lead is being implanted, the lead must be passed from the right atrium into the right ventricle through the tricuspid valve. Due the anatomy of the right ventricle, it is necessary to remove the straight stylet and then introduce a curved tip stylet, which the physician fashions manually from a standard straight stylet, so that the lead will have an appropriate shape, turn appropriately and pass through the tricuspid valve.
In the case where the lead does not have a screw fixation and is passive or has tines on the lead tip, the lead is then left in a visually appropriate position as determined by fluoroscopy and electrical testing is performed to confirm proper electrical contact. In the case of an active fixation lead, namely one having a screw-in-type tip, the attachment mechanism is then activated to secure the distal tip of the pacing lead into the endocardium at the selected position.
In a typical pacemaker implantation therefor, there are multiple exchanges of straight stylets and curved stylets which have been bent according to the physician's choice. The stylet is a thin solid wire, typically of about 0.014-0.018 inch in diameter. During handing, they can easily become bent or kinked, and thereafter cause great difficulty when an attempt is made to reinsert them through the narrow inner diameter of the lead's lumen, which may only be 0.019 inch in the case of a stylet of 0.018 inch or less diameter, typically providing no more than 0.0005 inch clearance on each side.
In addition, because the surgeon is working through an open wound, even the most fastidious surgeon will have blood on his gloves which will be transferred to the stylet. The blood congeals, and because of the small clearance, even a few drops of blood is sufficient to causing jamming of the stylet inside the lead body. When the stylet jams in the lead body, kinking of the stylet within the lead can occur, which kinks, in turn, will create new jams or problems with the insertion and retraction of the stylet from the lead.
The overall result of such difficulties is that operative time is greatly increased which results in much higher X-ray exposures to the patient, who is under continuos fluoroscopy, including scattered X-ray exposure to the operating room staff, increased cost due to procedural time delays, and in some cases, the jamming is so severe that the cardiac lead must be removed from the heart for fear of insulation puncture, discarded and a new lead implanted, thereby at least doubling the lead cost used in the procedure as well as operative time.
Therefore, what is needed is some type of apparatus or method that eliminates the need for any stylet removal or hand fashioning of a curve in a stylet by the physician, and which therefore will dramatically shorten X-ray risks to the patient and to the staff. The method should dramatically reduce the total time of operation for a pacemaker implantation, thereby broadly reducing the cost of this procedure under national and private health care cost schedules.
The same methodology is used in placing transvenous defibrillating leads which, in essence, are large pacing leads positioned at the apex of the right ventricle.
The apparatus and method should be such that it is usable in both pediatric and adult patients with considerably different sized heart structures.
The apparatus and methodology should be applicable to any type of cardiac implantation used, including the atrial and ventricular placements with both passive and active fixation and any type of device that utilizes a lead or catheter.